Systemic Administration Of Mesenchymal Stem Cells Research Articles

Mesenchymal Stem Cell Engagement Modulates Neuroma Microenviroment in Rats and Humans and Prevents Postamputation Pain

Postamputation pain is currently managed unsatisfactorily with neuron-targeted pharmacological and interventional therapies. Non-neuronal pain mechanisms have emerged as crucial factors in the development and persistence of postamputation pain. Consequently, these mechanisms offer exciting prospects as innovative therapeutic targets. We examined the hypothesis that engaging mesenchymal stem cells (MSCs) would foster local neuroimmune interactions, leading to a potential reduction in postamputation pain. We utilized an ex vivo neuroma model from a phantom limb pain patient to uncover that the oligodeoxynucleotide IMT504 engaged human primary MSCs to promote an anti-inflammatory microenvironment. Reverse translation experiments recapitulated these effects. Thus, in an in vivo rat model, IMT504 exhibited strong efficacy in preventing autotomy (self-mutilation) behaviors. This effect was linked to a substantial accumulation of MSCs in the neuroma and associated dorsal root ganglia and the establishment of an anti-inflammatory phenotype in these compartments. Centrally, this intervention reduced glial reactivity in the dorsal horn spinal cord, demonstrating diminished nociceptive activity. Accordingly, the exogenous systemic administration of MSCs phenocopied the behavioral effects of IMT504. Our findings underscore the mechanistic relevance of MSCs and the translational therapeutic potential of IMT504 to engage non-neuronal cells for the prevention of postamputation pain. PerspectiveThe present study suggests that IMT504-dependent recruitment of endogenous MSCs within severely injured nerves may prevent post-amputation pain by modifying the inflammatory scenario at relevant sites in the pain pathway. Reinforcing data in rat and human tissues supports the potential therapeutic value of IMT504 in patients suffering postamputation pain.

Efficacy of Rectal Systemic Administration of Mesenchymal Stem Cells to Injury Sites via the CXCL12/CXCR4 Axis to Promote Regeneration in a Rabbit Skeletal Muscle Injury Model.

Mesenchymal stem cells (MSCs) have been transplanted directly into lesions or injected intravenously. The administration of MSCs using these delivery methods requires specialized knowledge, techniques, and facilities. Here, we describe intrarectal systemic administration of MSCs, a simple, non-invasive route for homing to the injury sites to promote the regeneration of skeletal muscle injuries. Using a cardiotoxin (CTX)-induced rabbit skeletal muscle injury model, homing to the site of muscle injury was confirmed by intrarectal administration of MSCs; the time required for homing after intrarectal administration was approximately 5 days. In addition, the C-X-C chemokine ligand 12 (CXCL12)/C-X-C chemokine receptor-4 (CXCR4) axis was found to be involved in the homing process. Histopathological examinations showed that skeletal muscle regeneration was promoted in the MSCs-administered group compared to the CTX-only group. Myosin heavy polypeptide 3 (Myh3) expression, an indicator of early muscle regeneration, was detected earlier in the intrarectal MSCs group compared to the CTX-only group. These findings indicate that intrarectal administration of MSCs is effective in homing to the injured area, where they promote injury repair. Since intrarectal administration is a simple and non-invasive delivery route, these findings may be valuable in future research on stem cell therapy.

Reversal of Neuropsychiatric Comorbidities in an Animal Model of Temporal Lobe Epilepsy Following Systemic Administration of Dental Pulp Stem Cells and Bone Marrow Mesenchymal Stem Cells.

We aim to investigate whether timed systemic administration of dental pulp stem cells (DPSCs) or bone marrow mesenchymal stem cells (BM-MSCs) with status epilepticus (SE) induced blood-brain barrier (BBB) damage could facilitate the CNS homing of DPSCs/BM-MSCs and mitigate neurodegeneration, neuroinflammation and neuropsychiatric comorbidities in an animal model of Temporal Lobe epilepsy (TLE). Cognitive impairments, altered emotional responsiveness, depression, and anxiety are the common neuropsychiatric co-morbidities observed in TLE patients. Mesenchymal stem cells (MSCs) transplantation has gained immense attention in treating TLE, as ~30% of patients do not respond to anti-epileptic drugs. While MSCs are known to cross the BBB, better CNS homing and therapeutic effects could be achieved when the systemic administration of MSC is timed with BBB damage following SE. The objectives of the present study are to investigate the effects of systemic administration of DPSCs/BM-MSCs timed with BBB damage on CNS homing of DPSCs/BM-MSCs, neurodegeneration, neuroinflammation and neuropsychiatric comorbidities in an animal model of TLE. We first assessed the BBB leakage following kainic acid-induced SE and timed the intravenous administration of DPSCs/BM-MSCs to understand the CNS homing/engraftment potential of DPSCs/BM-MSCs and their potential to mitigate neurodegeneration, neuroinflammation and neuropsychiatric comorbidities. Our results revealed that systemic administration of DPSCs/BM-MSCs attenuated neurodegeneration, neuroinflammation, and ameliorated neuropsychiatric comorbidities. Three months following intravenous administration of DPSCs/BM-MSCs, we observed a negligible number of engrafted cells in the corpus callosum, sub-granular zone, and sub-ventricular zone. Thus, it is evident that functional recovery is still achievable despite poor engraftment of MSCs into CNS following systemic administration.

Repeated intravenous infusion of mesenchymal stem cells for enhanced functional recovery in a rat model of chronic cerebral ischemia.

Stroke is a major cause of long-term disability, and there are few effective treatments that improve function in patients during the chronic phase of stroke. Previous research has shown that single systemic infusion of mesenchymal stem cells (MSCs) improves motor function in acute and chronic cerebral ischemia models in rats. A possible mechanism that could explain such an event includes the enhanced neural connections between cerebral hemispheres that contribute to therapeutic effects. In the present study, repeated infusions (3 times at weekly intervals) of MSCs were administered in a rat model of chronic stroke to determine if multiple dosing facilitated plasticity in neural connections. The authors induced middle cerebral artery occlusion (MCAO) in rats and, 8 weeks thereafter, used them as a chronic stroke model. The rats with MCAO were randomized and intravenously infused with vehicle only (vehicle group); with MSCs at week 8 (single administration: MSC-1 group); or with MSCs at weeks 8, 9, and 10 (3 times, repeated administration: MSC-3 group) via femoral veins. Ischemic lesion volume and behavioral performance were examined. Fifteen weeks after induction of MCAO, the thickness of the corpus callosum (CC) was determined using Nissl staining. Immunohistochemical analysis of the CC was performed using anti-neurofilament antibody. Interhemispheric connections through the CC were assessed ex vivo by diffusion tensor imaging. Motor recovery was better in the MSC-3 group than in the MSC-1 group. In each group, there was no change in the ischemic volume before and after infusion. However, both thickness and optical density of neurofilament staining in the CC were greater in the MSC-3 group, followed by the MSC-1 group, and then the vehicle group. The increased thickness and optical density of neurofilament in the CC correlated with motor function at 15 weeks following induction of MCAO. Preserved neural tracts that ran through interhemispheric connections via the CC were also more extensive in the MSC-3 group, followed by the MSC-1 group and then the vehicle group, as observed ex vivo using diffusion tensor imaging. These results indicate that repeated systemic administration of MSCs over 3 weeks resulted in greater functional improvement as compared to single administration and/or vehicle infusion. In addition, administration of MSCs is associated with promotion of interhemispheric connectivity through the CC in the chronic phase of cerebral infarction.

Effects of Systemic or Local Administration of Mesenchymal Stem Cells from Patients with Osteoporosis or Osteoarthritis on Femoral Fracture Healing in a Mouse Model.

The purpose of this study was to analyze the regenerative capacity of mesenchymal stem cells (MSCs) in the treatment of fractures. MSCs extracted from patients with osteoporotic hip fractures or hip osteoarthritis undergoing hip replacement surgeries were cultured and injected into mice with femoral fracture. Two experimental models were established, one for the systemic administration of MSCs (n = 29) and another one for local administration (n = 30). Fracture consolidation was assessed by micro-CT and histology. The degree of radiological consolidation and corticalization was better with MSCs from osteoporosis than from osteoarthritis, being significant after systemic administration (p = 0.0302 consolidation; p = 0.0243 corticalization). The histological degree of consolidation was also better with MSCs from osteoporosis than from osteoarthritis. Differences in histological scores after systemic infusion were as follows: Allen, p = 0.0278; Huo, p = 0.3471; and Bone Bridge, p = 0.0935. After local administration at the fracture site, differences in histological scores were as follows: Allen, p = 0.0764; Huo, p = 0.0256; and Bone Bridge, p = 0.0012. As osteoporosis and control groups were similar, those differences depended on an inhibitory influence by MSCs from patients with osteoarthritis. In conclusion, we found an unexpected impairment of consolidation induced by MSCs from patients with osteoarthritis. However, MSCs from patients with osteoporosis compared favorably with cells from patients with osteoarthritis. In other words, based on this study and previous studies, MSCs from patients with osteoporosis do not appear to have worse bone-regenerating capabilities than MSCs from non-osteoporotic individuals of similar age.

Coagulopathy As a Dose-Limiting Toxicity in Systemic Administration of Mesenchymal Stem Cells (MSCs): Relative Safety of Bone Marrow Versus Adipose Derived MSCs

Introduction: Systemic administration of mesenchymal stem cells (MSCs) is an option that allows MSCs to interact with circulatory immune cells, or to deliver MSCs into multiple traumatic sites that are not reachable through regional delivery. The number of MSCs per injection also needs to be determined in order to achieve the maximal beneficial effect, and optimize the ratio of MSCs to target cells. However, MSCs express tissue factor, which is known to activate coagulation, which could potentially cause inappropriate clot formation, counteracting the beneficial effect of MSCs on tissue regeneration and immunomodulation at the site of injury. In this study, we sought to determine the maximum dose of MSCs that can safely be used for systemic administration by measuring their impact on coagulation in rats.Method: Bone marrow and adipose derived MSCs (BMSC and AMSC) were isolated from bone (femur and tibia) and visceral fat tissue, respectively, in normal young Sprague Dawley (SD) rats. Both BMSCs and AMSCs were cultured and passaged using Dulbecco's Modified Eagle's Medium (DMEM) with 20% fetal bovine serum. MSCs at passage 2-5 were labeled with green fluorescent chloromethyl derivatives of fluorescein diacetate (CMFDA), resuspended in normal saline with anticoagulant (Citrate Phosphate Dextrose (CPD)), and infused into the SD rats through the femoral vein at doses of 2.5, 5, 10, 20, and 40 million/kg under anesthesia. Citrated whole blood was collected at the base line, immediately after infusion, 1 hour, and 3 hours after infusion of MSCs. The prothrombin time (PT), activated partial thromboplastin time (aPTT) and fibrinogen were measured by hemostasis analyzer (ST4); coagulation properties and platelet aggregation (response to ADP (Adenosine Diphosphate) and collagen) were measured by hemostasis analyzer, rotational thromboelastometry (ROTEM) and impedance aggregometry (Multiplate), respectively. The MSCs in circulation were measured by flow cytometry. The MSCs in tissue were determined by histology.Results: At the dose of 20 million/kg, rats survived with BMSCs, but died with AMSCs (n=3 per group). Two of three rats survived with infusion of BMSCs at 40 million/kg. The platelet counts were significantly reduced at 1hr after MSC infusion (%change to baseline: AMSCs: -4±0; -24±3; -39±8 % at 2.5, 5 and 10 million/kg, respectively; BMSCs: -3±0, -4±3, -18±4, -19±6, -63±5 % at 2.5, 5, 10, 20 and 40 million/kg, respectively). Both PT and aPTT were significantly prolonged (PT: 35±4(AMSC) vs. 9±3(BMSC)% increased; aPTT 81±6(AMSC) vs. 17±3(BMSC)% increased), and fibrinogen levels significantly declined (-39±8(AMSC) vs. -18±4(BMSC)% decreased) after 10 million/kg AMSC or BMSC infusion. In comparison to the baseline, clotting time (CT) was significantly prolonged (AMSCs: 124±14 (vs. 68±6); BMSCs: 82±8 (vs. 57±4) seconds), and maximum clot firmness (MCF) was significantly reduced (AMSC: 39±3 (vs. 58±2) mm); BMSCs: 38±7 (vs. 62±4) mm) at 1hr after infusion of AMSCs at 10 million/kg or BMSCs at 20 million/kg respectively. Platelet aggregation (area under the curve (mm2)) significantly declined compared to the baseline after infusion of 10 million/kg AMSCs (ADP: 10±4 (vs. 75±7.0); Collagen: 4±4 (vs. 74±5)) or 20 million/kg BMSCs (ADP: 20±15 (vs. 89±12); Collagen: 36±18 (vs.102±10)). There were few circulating AMSCs or BMSCs found after 1 and 3 hours after infusion. The MSCs were found mostly in the lung, as determined by histology.Conclusion: AMSCs and BMSCs are not maintained in the circulation after systemic administration. However, infusion of MSCs has a significant impact on the hemostatic system, as shown by prolongation of PT, aPTT, and CT; and a decrease in fibrinogen levels, platelet counts, platelet function, and clot firmness. These data suggest that systemic administration of MSCs has a potential risk of causing consumptive coagulopathy, which may be initiated by the tissue factor expression of MSCs. This study also suggests that BMSCs have less impact than AMSCs on hemostasis, and BMSCs at the dose of 5 million/kg or less has the least risk of causing coagulopathy. Future studies are necessary to investigate the appropriate methods of down-regulating the procoagulant properties of MSCs prior to systemic administration in order to minimize the potential risk of coagulopathy. DisclosuresNo relevant conflicts of interest to declare.

The Altered Migration and Distribution of Systemically Administered Mesenchymal Stem Cells in Morphine-Treated Recipients.

Mesenchymal stem cells (MSCs) have the ability to migrate to the site of injury or inflammation, and to contribute to the healing process. Since patients treated with MSCs are often users of analgesic drugs, to relieve their uncomfortable pain associated with the tissue disorder, there is a possibility of negative effects of these drugs on the migration of endogenous and exogenous MSCs. Therefore, we tested the impact of acute and chronic treatment with morphine on the migration and organ distribution of exogenous adipose tissue-derived MSCs in mouse models. Firstly, we showed that the incubation of MSCs with morphine significantly reduced the expression of adhesive molecules CD44 (HCAM), CD54 (ICAM-1) and CD106 (VCAM-1) on MSCs. Using a model of systemic administration of MSCs labeled with vital dye PKH26 and by the application of flow cytometry to detect living CD45-PKH26+ cells, we found a decreased number of labeled MSCs in the lung, spleen and bone marrow, and a significantly increased number of MSCs in the liver of morphine-treated recipients. A skin allograft model was used to study the effects of morphine on the migration of exogenous MSCs to the superficial wound. Intraperitoneally administered MSCs migrated preferentially to the wound site, and this migration was significantly decreased in the morphine-treated recipients. The present results showed that morphine significantly influences the distribution of exogenous MSCs in the body, and decreases their migration to the site of injury.

Intraperitoneal infusion of mesenchymal stem cell attenuates severity of collagen antibody induced arthritis.

It is unclear how systemic administration of mesenchymal stem cells (MSCs) controls local inflammation. The aim of this study was to evaluate the therapeutic effects of human MSCs on inflammatory arthritis and to identify the underlying mechanisms. Mice with collagen antibody-induced arthritis (CAIA) received two intraperitoneal injections of human bone marrow-derived MSCs. The clinical and histological features of injected CAIA were then compared with those of non-injected mice. The effect of MSCs on induction of regulatory T cells was examined both in vitro and in vivo. We also examined multiple cytokines secreted by peritoneal mononuclear cells, along with migration of MSCs in the presence of stromal cell-derived factor-1 alpha (SDF-1α) and/or regulated on activation, normal T cell expressed and secreted (RANTES). Sections of CAIA mouse joints and spleen were stained for human anti-nuclear antibodies (ANAs) to confirm migration of injected human MSCs. The results showed that MSCs alleviated the clinical and histological signs of synovitis in CAIA mice. Peritoneal lavage cells from mice treated with MSCs expressed higher levels of SDF-1α and RANTES than those from mice not treated with MSCs. MSC migration was more prevalent in the presence of SDF-1α and/or RANTES. MSCs induced CD4+ T cells to differentiate into regulatory T cells in vitro, and expression of FOXP3 mRNA was upregulated in the forepaws of MSC-treated CAIA mice. Synovial and splenic tissues from CAIA mice receiving human MSCs were positive for human ANA, suggesting recruitment of MSCs. Taken together, these results suggest that MSCs migrate into inflamed tissues and directly induce the differentiation of CD4+ T cells into regulatory T cells, which then suppress inflammation. Thus, systemic administration of MSCs may be a therapeutic option for rheumatoid arthritis.

Mesenchymal Stem Cell-Derived Exosomes Stimulate Cycling Quiescence and Early Breast Cancer Dormancy in Bone Marrow.

Dormant breast cancers resurge as metastatic disease after a long dormancy period in the bone marrow, where cancer cells interact with mesenchymal stem cells (MSC). However, the nature of early interactions between breast cancer cells and MSCs in the bone marrow microenvironment that facilitate adaptation to a quiescent state remains poorly understood. Here, we report that breast cancer cells prime MSC to release exosomes containing distinct miRNA contents, such as miR-222/223, which in turn promotes quiescence in a subset of cancer cells and confers drug resistance. Building on these results, we developed a novel, nontoxic therapeutic strategy to target dormant breast cancer cells based on systemic administration of MSC loaded with antagomiR-222/223. In an immunodeficient mouse model of dormant breast cancer, this therapy sensitized breast cancer cells to carboplatin-based therapy and increased host survival. Overall, our findings illuminate the nature of the regulatory interactions between breast cancer cells and MSCs in the evolution of tumor dormancy and resurgence in the micrometastatic microenvironment of the bone marrow. Cancer Res; 76(19); 5832-44. ©2016 AACR.

Benefits of mesenchymal stem cells after partial bladder outlet obstruction

Partial bladder outlet obstruction (pBOO) results in significant morbidity and mortality in the pediatric and adult populations. Mesenchymal stem cells (MSC) have been widely studied in many organ systems for the treatment and prevention of fibrotic and inflammatory conditions. Therefore, we hypothesize that systemic administration of MSC will demonstrate short-term biochemical, histological, and urodynamic benefits in an animal model for pBOO. After University ethics approval, 5 × 106 green fluorescent protein GFP-labeled MSC were intravenously injected concurrently with pBOO in adult Sprague-Dawley rats. Five groups (n=3/group) were analyzed: a) unobstructed controls; b) pBOO for seven days with intravenous MSC (7d+MSC); c) pBOO for seven days without intravenous MSC (7d-MSC); d) pBOO for 14 days with intravenous MSC (14d+MSC), e) pBOO for 14 days without MSC (14d-MSC). Urodynamics were performed at the end of the experimental period and bladders were weighed. Immunohistochemistry was performed for GFP detection and reverse transcription polymerase chain reaction (RT-PCR) to detect mRNA of: TGF-B, HIF-1a, RhoA, GRP-78, lumican, and decorin. All animals remained healthy. GFP was detected in all treatment groups. MSC treatment resulted in a significant decrease in bladder capacity (0.91 cc vs. 2.15 cc, p=0.04). Treatment also resulted in significant decreases in mRNA levels of: TGF-B, HIF-1a, Rho-A, and GRP-78. Systemic treatment with MSC was well tolerated and resulted in MSC accumulation after pBOO. Despite our low numbers, we were able to successfully demonstrate short-term urodynamic improvements and widespread, significant decreases in inflammatory mediators. We believe that this decreased inflammatory cascade will help prevent long-term detrusor deterioration.

Stromal Cell-Derived Factor 1α-Stimulated Mesenchymal Stem Cells Confer Enhanced Protection Against Light-Induced Retinal Degeneration in Rats

Purpose: Mesenchymal stem cells (MSCs) are currently considered to be modulators of repair in various tissues. After MSC transplant, photoreceptor rescue has been demonstrated in models of retinal degeneration. Herein, we evaluate the roles of MSCs in modulating the host reaction and photoreceptor preservation in rats suffering from light-induced retinal degeneration.Methods: Unstimulated and stromal cell-derived factor 1α (SDF-1α)-stimulated MSCs were intravenously transplanted into light-injured rats. Their photoreceptor rescue effect was compared with untreated light-injured rats and light-injured rats received only medium injection. Ciliary neurotrophic factor (CNTF) and glial fibrillary acidic protein (GFAP) expression was identified to assess host reaction post-transplantation. Retinal localization and integration of MSCs were determined by green fluorescence protein labeling.Results: MSCs were able to migrate and integrate into the host retina, and significantly inhibited retinal cell death. CNTF and GFAP were induced upregluation after MSC injection. SDF-1α stimulation elicited superior effects in both MSC migration and the inhibition of apoptosis. CNTF and GFAP expression in host retinas that received stimulated MSCs were stronger than in retinas that received unstimulated MSCs.Conclusions: Systemic administration of MSCs exerts a protective effect against light-induced retinal degeneration, and upregulates neurotrophin expression in the host retina. MSCs can be stimulated to enhance the therapeutic effect.

Could donor multipotent mesenchymal stromal cells prevent or delay the onset of diabetic retinopathy?

Diabetes mellitus is a complex metabolic disease that has become a global epidemic with more than 285 million cases worldwide. Major medical advances over the past decades have substantially improved its management, extending patients' survival. The latter is accompanied by an increased risk of developing chronic macro- and microvascular complications. Amongst them, diabetic retinopathy (DR) is the most common and frightening. Furthermore, during the past two decades, it has become the leading cause of visual loss. Irrespective of the type of diabetes, DR follows a well-known clinical and temporal course characterized by pericytes and neuronal cell loss, formation of acellular-occluded capillaries, occasional microaneurysms, increased leucostasis and thickening of the vascular basement membrane. These alterations progressively affect the integrity of retinal microvessels, leading to the breakdown of the blood-retinal barrier, widespread haemorrhage and neovascularization. Finally, tractional retinal detachment occurs leading to blindness. Nowadays, there is growing evidence that local inflammation and oxidative stress play pivotal roles in the pathogenesis of DR. Both processes have been associated with pericytes and neuronal degeneration observed early during DR progression. They may also be linked to sustained retinal vasculature damage that results in abnormal neovascularization. Currently, DR therapeutic options depend on highly invasive surgical procedures performed only at advanced stages of the disease, and which have proved to be ineffective to restore visual acuity. Therefore, the availability of less invasive and more effective strategies aimed to prevent or delay the onset of DR is highly desirable. Multipotent mesenchymal stromal cells, also referred to as mesenchymal stem cells (MSCs), are promising healing agents as they contribute to tissue regeneration by pleiotropic mechanisms, with no evidence of significant adverse events. Here, we revise the pathophysiology of DR to identify therapeutic targets for donor MSCs. Also, we discuss whether an MSC-based therapy could prevent or delay the onset of DR.

Mesenchymal stem cells are mobilized from the bone marrow during inflammation

Mesenchymal stem cells (MSCs) show great therapeutic potential for the treatment of various immune mediated diseases, including Multiple Sclerosis (MS). Systemic administration of MSCs during experimental allergic encephalomyelitis (EAE), an animal model for MS, was shown to reduce the infiltration of T cells, B cells, and macrophages into the CNS. Whether endogenous MSCs are mobilized and potentially modulate the severity of disease is not known. Here we show that during the acute phase of EAE, MSCs numbers in the bone marrow were severely reduced, which restored to control levels during the progressive phase of the disease. The number of bone marrow MSCs inversely correlated with the number of both CD4 and CD8 T cells present in the bone marrow indicating a link between activated T cells and MSC mobilization. Analysis of CD70-transgenic mice, which have a constitutively activated immune system and elevated number of activated T cells in the bone marrow, showed severely reduced number of bone marrow MSCs. Transfer of T cells that were activated through their CD27 receptor reduced the number of bone marrow MSCs dependent on IFN-y. These data provide a mechanism by which MSCs can be mobilized from the bone marrow in order to contribute to tissue repair at a distant location.

Effects of human umbilical cord-derived mesenchymal stem cells on anterior chamber-associated immune deviation

Introduction of antigen into anterior chamber (AC) induces a deviant immune response termed anterior chamber-associated immune deviation (ACAID) that protects the eye from inflammatory destruction consequent to a systemic immune response. Mesenchymal stem cells (MSCs) can modulate a variety of immune responses. However, the effects of systemic administration of MSCs on ACAID have not been explored. In this study, C57BL/6 mice were inoculated with ovalbumin in the AC to induce ACAID, control group received AC injection of solvent alone. Immediately after the AC injection, the mice were injected through the tail vein with human Umbilical Cord-derived MSCs (hUC-MSC) or phosphate buffer saline. All animals were subcutaneously immunized with ovalbumin one week later. Delayed-type hypersensitivity assay was performed another week following immunization. The splenic monocytes were then isolated, cultured and stimulated with ovalbumin. Levels of IL-10, TGF-β, and IFN-γ in culture media were measured by ELISA. The frequencies of CD4+CD25+Foxp3+ and CD8+Foxp3+ regulatory T cells (Tregs) were determined by flow cytometry. The results showed that the AC inoculation of ovalbumin induced significantly less ear swelling than controls, confirming the establishment of ACAID. MSCs potentiated IL-10 and TGF-β production, further suppressed IFN-γ secretion from splenic monocytes in ACAID mice, and enhanced expansion of CD4+CD25+Foxp3+ and CD8+Foxp3+ Tregs isolated from the spleen of ACAID mice. Therefore, our study, for the first time, provides clear evidence that systemic administration of MSCs augments cytokine production and Treg expansion from ACAID spleens, which may contribute to promotion and maintenance of ACAID.

Effect of mesenchymal stem cells on hypoxia-induced desensitization of β2-adrenergic receptors in rat osteosarcoma cells

The β2-adrenergic receptor (β2AR) mediates the effects of chronic stress in several neoplasms, however, β2AR signaling is impaired by hypoxia in various tissues. While hypoxia is a common feature significant in the progression of solid tumors, little is known about the effect of hypoxia on β2AR signaling in the tumor microenvironment. Previously, it has been reported that the systemic administration of mesenchymal stem cells (MSCs) increased the engraftment and metastatic colonization of rat osteosarcoma (OS) cells. In the current study, the effect of MSCs on the hypoxia-induced desensitization of the β2AR in OS cells was investigated. Epinephrine, norepinephrine and isoproterenol increased the cellular proliferation of the rat OS cell line COS1NR and rat MSCs in a dose-dependent and β2AR antagonist-sensitive manner. While isoproterenol had significant proliferative effects on MSCs under normoxic and hypoxic conditions, COS1NR cells did not respond under hypoxic conditions. A sensitivity assay for the β2AR revealed that hypoxia impaired the sensitivity of COS1NR cells, whereas hypoxia did not affect MSCs. An immunoassay revealed no significant change in the expression of hypoxia-inducible factor-1α (HIF1α) in COS1NR cells, whilst an immunoassay demonstrated a 15% increase in MSCs following isoproterenol stimulation. In COS1NR cells co-cultured with MSCs under hypoxic conditions, isoproterenol caused a significant increase in proliferation and this effect was inhibited by an anti-interleukin (IL)-6 antibody. A tumor formation assay in syngeneic rats revealed that the systemic administration of MSCs enhances the growth of OS and the effect of MSCs was inhibited by IL-6 neutralization. In conclusion, MSCs are resistant to the hypoxia-induced desensitization to β2AR. Hypoxia caused a siginificant desensitization of the β2AR in COS1NR cells alone, whereas MSCs may support tumor progression through cellular interactions.

Therapeutic potential of bone marrow-derived mesenchymal stem cells producing pigment epithelium-derived factor in lung carcinoma

Specific and efficient gene delivery to target cells and the subsequent expression of the RNA and protein is crucial to the success of gene-based therapy for cancer. Mesenchymal stem cells (MSCs) represent novel and efficient tools for delivery of therapeutic agents to tumor cells. In this study, we evaluated the potential of bone marrow-derived mesenchymal stem cells, genetically modified to express pigment epithelium-derived factor (PEDF) for the treatment of Lewis lung carcinoma (LLC). MSCs derived from murine bone marrow were efficiently engineered to express human PEDF by adenoviral transduction, and the expression and bioactivity of the transgenic protein from engineered MSCs were confirmed in vitro. Animal experiments showed that the systemic administration of MSCs treated with PEDF dramatically reduced the growth of LLC tumors and significantly prolonged survival. Immunohistochemistry analysis of the tumors from MSC-PEDF-treated animals indicated an increase in apoptosis and a decrease in microvessel density. ELISA showed that the group of MSCs treated with PEDF had relatively higher expression levels of PEDF in tumor tissue and lower levels in serum compared with the free Ad-PEDF group. These results suggest that MSCs have potential use as effective delivery of vehicles for therapeutic genes in the treatment of LLC.

Immunomodulatory properties of mesenchymal stem cells and their therapeutic applications

Mesenchymal stem cells (MSCs) are adult stem cells that can be isolated from most adult tissues, including bone marrow, adipose, liver, amniotic fluid, lung, skeletal muscle and kidney. The term MSC is currently being used to represent both mesenchymal stem cells and multipotent mesenchymal stromal cells. Numerous reports on systemic administration of MSCs leading to functional improvements based on the paradigm of engraftment and differentiation have been published. However, it is not only difficult to demonstrate extensive engraftment of cells, but also no convincing clinical results have been generated from phase 3 trials as of yet and prolonged responses to therapy have been noted after identification of MSCs had discontinued. It is now clear that there is another mechanism by which MSCs exert their reparative benefits. Recently, MSCs have been shown to possess immunomodulatory properties. These include suppression of T cell proliferation, influencing dendritic cell maturation and function, suppression of B cell proliferation and terminal differentiation, and immune modulation of other immune cells such as NK cells and macrophages. In terms of the clinical applications of MSCs, they are being tested in four main areas: tissue regeneration for cartilage, bone, muscle, tendon and neuronal cells; as cell vehicles for gene therapy; enhancement of hematopoietic stem cell engraftment; and treatment of immune diseases such as graft-versus-host disease, rheumatoid arthritis, experimental autoimmune encephalomyelitis, sepsis, acute pancreatitis and multiple sclerosis. In this review, the mechanisms of immunomodulatory effects of MSCs and examples of animal and clinical uses of their immunomodulatory effects are described.

The Role of Chemokines in Mesenchymal Stem Cell Homing to Myocardium

A growing body of preclinical evidence suggests that mesenchymal stem cells (MSCs) are effective for the structural and functional recovery of the infracted heart. Accordingly, clinical trials are underway to determine the benefit of MSC-based therapies. While systemic administration of MSCs is an attractive strategy, and is the route currently used for the administration of MSCs in clinical studies for myocardial infarction, the majority of infused cells do not appear to localize to infracted myocardium in animal studies. Recently, important progress has been made in identifying chemokine receptors critical for the migration and homing of MSCs. Here, we review recent literature regarding mechanisms of MSC homing and recruitment to the ischemic myocardium, and discuss potential influences of low engraftment rates of systemically administered MSCs to the infracted heart tissue on the effects of MSC-based therapies on myocardial infarction.

Combined Therapeutic Strategy Using Erythropoietin and Mesenchymal Stem Cells Potentiates Neurogenesis after Transient Focal Cerebral Ischemia in Rats

Many studies showed beneficial effects of either erythropoietin (EPO) or mesenchymal stem cells (MSCs) treatment in cerebral ischemia. In addition to a neuroprotective role, not only EPO but also MSC favors neurogenesis and functional recovery. In an attempt to further improve postischemic tissue repair, we investigated the effect of a systemic administration of MSC, in the presence or not of EPO, on neurogenesis and functional recovery in a transient focal cerebral ischemia model in the adult rat. Twenty-four hours after ischemia, the rats were divided into four groups, namely vehicle, MSC, EPO, and MSC+EPO, and received a single intravenous injection of MSC (2 x 10(6) cells) and/or a repeated intraperitoneal administration of EPO (1,000 UI/kg) for 3 days. The lesion volume, the MSC outcome, neurogenesis, and functional recovery were assessed 51 days after ischemia. The results showed that cellular proliferation and neurogenesis were increased along the lateral ventricle wall in the MSC+EPO group, whereas no significant effect was observed in groups receiving MSC or EPO alone. This effect was accompanied by an improvement of mnesic performances. Mesenchymal stem cells expressing neuronal or glial markers were detected in the ischemic hemisphere. These results suggest that EPO could act in a synergistic way with MSC to potentiate the postischemic neurogenesis.

Culturing of Human Mesenchymal Stem Cells as Three-dimensional Aggregates Induces Functional Expression of CXCR4 That Regulates Adhesion to Endothelial Cells

Culture-expanded human mesenchymal stem cells (hMSCs) are increasingly used in a variety of preclinical and clinical studies. However, these cells have a low rate of engraftment to bone marrow or damaged tissues. Several laboratories have shown that during isolation and subculturing mesenchymal stem cells quickly lose the expression of CXCR4, the key receptor responsible for lymphocytes and hematopoietic stem cell homing. Here we show that culturing of hMSCs as three-dimensional aggregates (hMSC spheroids) restores CXCR4 functional expression. Expression of CXCR4 inversely correlates with the secretion of SDF-1 by hMSCs. Cells from hMSC spheroids up-regulate expression of CD49b, the alpha2 integrin subunit, and suppress the expression of CD49d, the alpha4 integrin subunit. Transfer of cells from the spheroids back to a monolayer suppresses the expression of CXCR4 and CD49b and restores the expression of CD49d. Treatment of cells from the spheroids with SDF-1 leads to CXCR4 internalization and activation of ERK-1,2. Adhesion of hMSCs to human umbilical vein endothelial cells (HUVECs) was investigated. SDF-1, AMD-3100, or exposure of HUVECs to hypoxia did not affect adhesion of hMSCs from a monolayer to HUVECs. Adhesion of cells from hMSC spheroids to HUVECs was stimulated by SDF-1, AMD-3100, or by exposure of HUVECs to hypoxia. Stimulatory effects of hypoxia and addition of SDF-1 or AMD-3100 were not additive. Overall, our data indicate that the expression of CXCR4 by hMSCs regulates hMSC adhesion to endothelial cells.